Question

2. Corrosion in neutral medium Some item is made of two metals -zink and nickel which are in contact with each other. The item corrosion procesg ergoes corrosion process in neutral moisture containing environment. What metal is going to oxidize W hat chemical element (depolizer) is going to reduce? Write down redox equations for both processes: for metal: for depolizer -0.23 V 3. Protection metal against Corrosion (anodic coating) Opt right anodic coating for Pb from the following metals: Pt, Al, Cu, Hg You are given standard potential values Al+3e Al Cu +2e Cu ф,--1.70 V po- 0.34 V 90- 0.85 V Protection metal against Corrosion (cathodie coating) 4. Opt right cathodic coating for Pb from the following metals: Mn, Cr, Ag You are given standard potential values Po -0.13 V 1.19 v 0.74 V Ag teAg 0.80v

Answer 1

2) Since Zn has low reduction potential it get Oxidized and Ni get reduced.

For metal : Zn $\rightarrow$ Zn ²⁺ + 2e^-

For depolizer : Ni ²⁺ + 2e^-$\rightarrow$ Ni

3) At anode Oxidation takes place an element whose reduction potential is less than Pb will act as protection metal.

Answer is Al.

4) At cathode reduction takes place and an element with higher reduction potential than Pb will act as Cathodic protection. Answer is Ag.